Vane pump

ABSTRACT

A vane pump includes a cam ring, a rotor, a plurality of vane, and a lateral plate. The lateral plate has an extension groove. The shape of a pump chamber forming surface viewed from the rotation-axis direction of the rotor satisfies the following requirements i) and ii) at the time when a first vane passes the base end part of the extension groove: i) the center line of the groove width of the extension groove is inclined from the radial direction of the rotor; and ii) a slit in which a second vane is accommodated has an open end falling within a belt-shaped range obtained by extending a groove width of the base end part of the extension groove along a virtual extension line.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2020-171460 filed on Oct. 9, 2020, incorporated herein by reference in its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a vane pump.

2. Description of Related Art

A vane pump configured to discharge, from a discharge port, oil taken into an inlet port by a rotor rotating inside a rotor chamber is used for operation of a transmission or the like of a vehicle, for example. The rotor is configured such that vanes are accommodated in respective slits formed in a radial manner. In such a vane pump, when minute air bubbles included in the oil crush flatly due to an increase in pressure in an oil discharge step, erosion (cavitation damage) is caused by impact of the crush. In view of this, various measures to this erosion have been proposed.

In a vane pump described in Japanese Unexamined Patent Application Publication No. 2019-210881 (JP 2019-210881 A), a vane is provided with a recessed portion recessed in the plate-thickness direction of the vane such that the proportion of the volume of air bubbles to the volume of oil in a pump chamber is made small. Hereby, impact to be caused when the air bubbles crush flatly is relieved. Further, in a vane pump described in Japanese Unexamined Patent Application Publication No. 2018-123818 (JP 2018-123818 A), a plate-side pressurization groove communicating with a back-pressure groove is provided in a sideplate where an inlet port and a discharge port are formed, and a rotor-side pressurization groove extending radially is provided on a facing surface of a rotor, the facing surface facing the sideplate, so that a back pressure to push out a vane from a slit is introduced into a pump chamber from the back-pressure groove at the time when the plate-side pressurization groove communicates with the rotor-side pressurization groove. Hereby, a sudden increase in pressure inside the pump chamber is restrained, and occurrence of erosion is restrained.

SUMMARY

In the vane pump described in JP 2019-210881 A, when the recessed portion is deepened, the strength of the vane is affected. Further, in the vane pump described in JP 2018-123818 A, when the back pressure to be introduced into the pump chamber from the plate-side pressurization groove and the rotor-side pressurization groove is raised, such a problem might be caused that the pressure in the back-pressure groove decreases and the back pressure to push out the vane from the slit becomes insufficient. On this account, these measures might not necessarily yield a sufficient effect to restrain erosion depending on the specification such as a required discharge pressure, a required discharge amount, or the like.

In view of this, the present disclosure provides a vane pump that can restrain occurrence of erosion more effectively.

An aspect of the present disclosure is a vane pump. The vane pump includes a cam ring, a rotor, a plurality of vanes, and a lateral plate. The cam ring has a cam surface on an inner peripheral surface of the cam ring, and the cam ring forms a rotor chamber. The rotor is configured to rotate in a predetermined rotation direction inside the rotor chamber. The rotor includes a plurality of slits formed in a radial manner to extend radially outwardly from a central part of the rotor. The vanes are provided such that the vanes are accommodated in the slits, respectively, and rotate together with the rotor. The vanes are configured to define a plurality of pump chambers between the cam surface and an outer peripheral surface of the rotor. The lateral plate has a flat pump chamber forming surface facing the pump chambers. The lateral plate is configured such that an inlet port via which a fluid is taken into the rotor chamber and a discharge port via which the fluid taken into the rotor chamber is discharged are opened on the pump chamber forming surface. The lateral plate has an extension groove extended rearward in the rotation direction from the discharge port. The extension groove has a groove width gradually narrowed from a base end part, on the discharge port side, of the extension groove toward a distal end part of the extension groove. At the time when a first vane out of paired vanes defining a pump chamber communicating with the extension groove, the first vane being on the front side in the rotation direction of the rotor, passes the base end part of the extension groove, the pump chamber forming surface viewed from the rotation-axis direction of the rotor has a shape satisfying the following requirements i) and ii). i) A center line of the groove width of the extension groove is inclined from the radial direction of the rotor such that the center line approaches a rotation axis of the rotor on the distal end part side rather than the base end part side. ii) Among the slits, a slit in which a second vane out of the paired vanes, the second vane being on a rear side in the rotation direction, is accommodated has an open end falling within a belt-shaped range obtained by extending a groove width of the base end part of the extension groove along a virtual extension line obtained by further extending a center line of the groove width of the extension groove from the distal end part.

With the above configuration, it is possible to restrain occurrence of erosion.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:

FIG. 1 is a configuration diagram illustrating a schematic configuration of a vane pump according to an embodiment of the present disclosure;

FIG. 2 is a sectional view of the vane pump taken along a line II-II in FIG. 1;

FIG. 3A is a plan view illustrating a rotor;

FIG. 3B is a perspective view illustrating part of the rotor together with a vane;

FIG. 4 is a plan view illustrating a sideplate and a cam ring of the vane pump;

FIG. 5A is a perspective view illustrating the sideplate;

FIG. 5B is a perspective view illustrating a housing cover;

FIG. 6A is a partial enlarged view of FIG. 1 and illustrates a first extension groove and its peripheral part;

FIG. 6B is an enlarged view illustrating a part VIB in FIG. 6A in a further enlarged manner;

FIG. 7A is a configuration diagram illustrating part of a vane pump according to a comparative example; and

FIG. 7B is an enlarged view illustrating a part VIIB in FIG. 7A in an enlarged manner.

DETAILED DESCRIPTION OF EMBODIMENTS Embodiment

An embodiment of the present disclosure will be described below with reference to FIGS. 1 to 6B. Note that the following embodiment is described as a preferred concrete example on performing the present disclosure. There are some parts that specifically describe various technical matters that are technically preferable, but the technical scope of the present disclosure is not limited to such a concrete example.

FIG. 1 is a configuration diagram illustrating a schematic configuration of a vane pump according to the embodiment of the present disclosure. FIG. 2 is a sectional view of the vane pump taken along a line II-II in FIG. 1. FIG. 3A is a plan view illustrating a rotor, and FIG. 3B is a perspective view illustrating part of the rotor together with a vane. FIG. 4 is a plan view illustrating a sideplate and a cam ring of the vane pump. FIG. 5A is a perspective view illustrating the sideplate, and FIG. 5B is a perspective view illustrating a housing cover.

The vane pump 1 is, for example, attached to a transmission configured change the output rotation of a drive source (an engine) of an automobile in accordance with a vehicle speed or the like and is configured to take in and discharge transmission oil. The transmission oil thus discharged is used for lubrication of each part of the transmission or an operation of an actuator of the transmission. The transmission oil is one example of a fluid in the present disclosure. Hereinafter, the transmission oil is just referred to as oil.

Configuration of Vane Pump

The vane pump 1 includes a pump housing 2, a cam ring 3 and a sideplate (lateral plate) 4 accommodated in the pump housing 2, a rotor 5 rotatably accommodated in a rotor chamber 30 inside the cam ring 3, a plurality of plate-shaped vanes 6 configured to rotate together with the rotor 5, and a pump shaft 7 connected to the rotor 5 in a relatively non-rotatable manner.

The pump shaft 7 rotates upon receipt of rotary force of the engine as a drive source. The rotor 5 rotates in a predetermined rotation direction (an arrow-a direction illustrated in FIG. 1) around a rotation axis O of the rotor 5 together with the pump shaft 7. Hereinafter, a direction parallel to the rotation axis O of the rotor 5 is referred to as an axial direction. Further, the rotation direction of the rotor 5 as indicated by the arrow a is just referred to as a rotation direction.

As illustrated in FIG. 2, the pump housing 2 includes a housing main body 21 in which an accommodation space 20 is formed, and a housing cover 22 configured to close an opening of the accommodation space 20 in the housing main body 21. The housing main body 21 is fastened to the housing cover 22 by a plurality of bolts 23. The bolts 23 are threadedly engaged to threaded holes 21 a (see FIG. 1) provided in the housing main body 21. The housing main body 21 and the housing cover 22 are made of an aluminum-based metallic material (aluminum alloy), for example, and are molded by die-casting. In FIG. 1, the inside of the accommodation space 20 is illustrated without the housing cover 22.

The cam ring 3 and the sideplate 4 are accommodated in the accommodation space 20, and the rotor 5 is accommodated inside the cam ring 3. The sideplate 4 is placed such that its back face 4 b faces a bottom face 20 a of the accommodation space 20, and the cam ring 3 and the rotor 5 are placed between the sideplate 4 and the housing cover 22. The cam ring 3 and the sideplate 4 are made of an iron-based metallic material, for example, and are molded by sintering.

As illustrated in FIG. 2, first and second introduction portions 211, 212 into which the oil is introduced from an intake passage 210 are formed in the housing main body 21 such that they communicate with the accommodation space 20. Further, first and second discharge passages 213, 214 opened on the bottom face 20 a of the accommodation space 20 are formed in the housing main body 21. The vane pump 1 is configured to send the oil supplied to the first and second introduction portions 211, 212 to an oil-supply target from the first and second discharge passages 213, 214 by increasing the pressure of the oil. The oil sucked up from an oil pan (not illustrated) is introduced into the intake passage 210. Minute air bubbles may be mixed in this oil.

The pump shaft 7 is passed through an insertion hole 216 formed in the housing main body 21 and an insertion hole 40 formed in the sideplate 4, and a first end part of the pump shaft 7 is accommodated in a blind hole 220 formed in the housing cover 22. Further, the pump shaft 7 is rotatably supported by a bearing 81 accommodated in the insertion hole 216 of the housing main body 21 and a bearing 82 accommodated in the blind hole 220 of the housing cover 22.

The cam ring 3 has an outer peripheral surface formed in a round shape and an inner peripheral surface formed in an elliptical shape when the cam ring 3 is viewed in the axial direction. The inner peripheral surface is a cam surface 3 a with which distal end parts of the vanes 6 are to abut. A rotor chamber 30 in which the rotor 5 is placed is formed inside the cam ring 3 surrounded by the cam surface 3 a. The cam ring 3 has a pair of through-holes 31. A pair of pins 215 is formed in a standing manner on the bottom face 20 a of the accommodation space 20 in the housing main body 21 such that the pins 215 are passed through the through-holes 31, respectively. Further, a pair of through-holes 400 (illustrated in FIG. 5A) is formed in the sideplate 4, and the pins 215 are also passed through the through-holes 400, respectively. Hereby, the cam ring 3 and the sideplate 4 are non-rotatable relative to the pump housing 2.

As illustrated in FIGS. 1, 4, the sideplate 4 includes a first inlet port 41, a second inlet port 42, a first discharge port 43, and a second discharge port 44 formed such that they are arranged in the rotation direction of the rotor 5. The first inlet port 41 communicates with the first introduction portion 211, and the second inlet port 42 communicates with the second introduction portion 212. The first discharge port 43 communicates with the first discharge passage 213, and the second discharge port 44 communicates with the second discharge passage 214. The first and second inlet ports 41, 42 and the first and second discharge ports 43, 44 are opened on a flat pump chamber forming surface 4 a of the sideplate 4 facing the rotor chamber 30 such that the first and second inlet ports 41, 42 and the first and second discharge ports 43, 44 are formed to be axially recessed from the pump chamber forming surface 4 a. The pump chamber forming surface 4 a is a flat surface having no projection and recess and perpendicular to the axial direction.

Further, a first extension groove 45 communicating with the first discharge port 43 and a second extension groove 46 communicating with the second discharge port 44 are formed in the sideplate 4. The first extension groove 45 is extended further rearwardly in the rotation direction from a rear end part, in the rotation direction, of the first discharge port 43. The second extension groove 46 is extended further rearwardly in the rotation direction from a rear end part, in the rotation direction, of the second discharge port 44. Further, the passage area of the first extension groove 45 is gradually narrowed from its base end part on the first discharge port 43 side toward its distal end part. The passage area of the second extension groove 46 is gradually narrowed from its base end part on the second discharge port 44 side toward its distal end part.

Note that a general vane pump is also configured such that a groove extending rearward in the rotation direction of a rotor from a discharge port is formed in a sideplate. Such a groove is referred to as a “whisker groove,” for example, and restrains such a situation that erosion (cavitation damage) or noise occurs due to impact caused when air bubbles crush flatly due to a sudden increase in pressure of oil in a pump chamber. That is, the whisker groove has a function to restrain a sudden increase in pressure inside the pump chamber when the pump chamber communicates with a discharge port by introducing some oil into the pump chamber before the pump chamber directly communicates with the discharge port.

The rotor 5 is rotatably placed inside the rotor chamber 30 such that an outer peripheral surface 5 a of the rotor 5 faces the cam surface 3 a of the cam ring 3. The rotor 5 has a discoidal shape and is constituted by a sintered body obtained by burning powder made of iron-based metal, for example. A fitting hole 50 to which a spline portion 71 of the pump shaft 7 is fitted is formed in a central part of the rotor 5. The rotor 5 is non-rotatable relative to the pump shaft 7 and rotates together with the pump shaft 7. The pump chamber forming surface 4 a of the sideplate 4 faces a first side face 5 b of the rotor 5.

Further, as illustrated in FIG. 3A, the rotor 5 includes a plurality of slits 51 (12 slits 51 in the present embodiment) opened on the outer peripheral surface 5 a such that the slits 51 are formed in a radial manner directed radially outwardly from the central part of the rotor 5. The slits 51 are formed to have a width slightly larger than the thickness of the vanes 6 and penetrate through the rotor 5 in the axial direction. The vanes 6 are at least partially accommodated in the slits 51, respectively. The vanes 6 are movable in the radial direction of the rotor 5 by being guided by the slits 51.

Further, the rotor 5 is provided with back-pressure chambers 52 formed continuously from respective end parts, on the central part side, of the slits 51 such that the back pressure directed in a direction to push out the vanes 6 from the slits 51 radially outwardly is introduced into the back-pressure chambers 52. When the rotor 5 is viewed from the axial direction, the back-pressure chambers 52 are round holes with a diameter larger than the width of the slits 51, and the back-pressure chambers 52 penetrate through the rotor 5 in the axial direction.

An opening peripheral part of each of the slits 51 in the rotor 5 is formed as a protrusion 53 projecting radially outwardly from a circumferential central part between two adjacent slits 51 among the slits 51. Further, the circumferential central part between the two slits 51 adjacent to each other is formed as a recessed portion 54 recessed in the radial direction of the rotor 5 from the protrusion 53. A bottom face 54 a of the recessed portion 54 has an arcuate shape around the rotation axis O of the rotor 5. The protrusion 53 has a top surface 53 a on which the slit 51 is opened, and an inclined surface 53 b inclined from the top surface 53 a toward the bottom face 54 a of the recessed portion 54. The inclined surface 53 b is inclined gently from the radial direction of the rotor 5 between the top surface 53 a and the bottom face 54 a of the recessed portion 54.

Since the protrusions 53 are formed in the rotor 5, the slits 51 can be made long in comparison with a case where the whole outer peripheral surface 5 a is formed with a diameter between the bottom faces 54 a of the recessed portions 54, for example, and this makes it possible to restrain inclination of each of the vanes 6 due to a pressure difference between the pump chambers S adjacent to each other across the each of the vanes 6. Further, since the recessed portions 54 are formed in the rotor 5, the volume of the pump chamber S can be made large in comparison with a case where the whole outer peripheral surface 5 a is formed with a diameter between the top surfaces 53 a of the protrusions 53, for example, so that the proportion of the volume of air bubbles mixed into the oil to the volume of the pump chamber S is decreased. This makes it possible to relieve impact caused due to crush of the air bubbles.

The vanes 6 are made of metal such as high-carbon chrome steel that is harder than the rotor 5 or the sideplate 4, for example, and are formed in a flat plate shape. Upon receipt of the pressure (back pressure) of the oil introduced into the back-pressure chambers 52, respective distal end parts of the vanes 6 that project from the slits 51 abut with the cam surface 3 a. Inside the rotor chamber 30, a plurality of pump chambers S is defined by the vanes 6 between the outer peripheral surface 5 a of the rotor 5 and the cam surface 3 a. Here, to “define” indicates to form the pump chambers S by partitioning the rotor chamber 30. Respective projection amounts, from the slits 51, of the vanes 6 that define the pump chambers S communicating with the first and second inlet ports 41, 42 gradually increase along with the rotation of the rotor 5, and respective projection amounts, from the slits 51, of the vanes 6 that define the pump chambers S communicating with the first and second discharge ports 43, 44 gradually decrease along with the rotation of the rotor 5. The volumes of the pump chambers S change in accordance with the movement of the vanes 6 along with the rotation of the rotor 5.

In a course where the volume of the pump chamber S is increasing, the oil flows into the pump chamber S from the first inlet port 41 or the second inlet port 42, and in a course where the volume of the pump chamber S is decreasing, the oil thus flowing into the pump chamber S flows out to the first discharge port 43 or the second discharge port 44. The vane pump 1 discharges, from the first and second discharge ports 43, 44, the oil taken into the first and second inlet ports 41, 42 by volumetric changes in the pump chambers S along with the rotation of the rotor 5.

The sideplate 4 has first and second back pressure grooves 47, 48 formed on the pump chamber forming surface 4 a facing the side face 5 b of the rotor 5. The first back pressure groove 47 communicates with the back-pressure chambers 52 corresponding to the vanes 6 that define the pump chamber S in a first pressure transition stroke in which the oil taken in from the first inlet port 41 is discharged from the first discharge port 43. The second back pressure groove 48 communicates with the back-pressure chambers 52 corresponding to the vanes 6 that define the pump chamber S in a second pressure transition stroke in which the oil taken in from the second inlet port 42 is discharged from the second discharge port 44.

The first back pressure groove 47 includes a first intake-side back pressure groove portion 471 formed inside the first inlet port 41, a first discharge-side back pressure groove portion 472 formed inside the first discharge port 43, a first reduced portion 473 provided between the first intake-side back pressure groove portion 471 and the first discharge-side back pressure groove portion 472, and a first extending portion 474 extending rearward in the rotation direction from the first discharge-side back pressure groove portion 472. The first intake-side back pressure groove portion 471 communicates with the first discharge passage 213 via a communicating hole 401 (see FIG. 2) formed in the sideplate 4.

Similarly, the second back pressure groove 48 includes a second intake-side back pressure groove portion 481 formed inside the second inlet port 42, a second discharge-side back pressure groove portion 482 formed inside the second discharge port 44, a second reduced portion 483 provided between the second intake-side back pressure groove portion 481 and the second discharge-side back pressure groove portion 482, and a second extending portion 484 extending rearward in the rotation direction from the second discharge-side back pressure groove portion 482. The second intake-side back pressure groove portion 481 communicates with the second discharge passage 214 via a communicating hole 402 (see FIG. 2) formed in the sideplate 4.

A first recessed portion 221 facing the first discharge port 43 in the axial direction, a second recessed portion 222 facing the second discharge port 44 in the axial direction, a third recessed portion 223 facing the first extension groove 45 in the axial direction, a fourth recessed portion 224 facing the second extension groove 46 in the axial direction, a fifth recessed portion 225 facing the first back pressure groove 47 in the axial direction, and a sixth recessed portion 226 facing the second back pressure groove 48 in the axial direction are formed on a flat surface 22 a of the housing cover 22, the flat surface 22 a being formed on the rotor chamber 30 side. With the configuration of the housing cover 22, force to be received on the housing cover 22 side of the rotor 5 and the vanes 6 by the pressure of the oil is balanced with force to be received on the sideplate 4 side of the rotor 5 and the vanes 6 by the pressure of the oil, so that the rotation of the rotor 5 and the vanes 6 is facilitated.

The pressure inside the pump chamber S suddenly increases when the pump chamber S communicates with the first discharge port 43 or the second discharge port 44. At this time, when many air bubbles are mixed in the oil inside the pump chamber S, the air bubbles crush to cause impact. When erosion occurs on the pump chamber forming surface 4 a of the sideplate 4 due to the impact, a seal effect to prevent the flow of the oil between the pump chambers S adjacent to each other might decrease.

In the course of diligently examining a configuration of a vane pump to restrain erosion, the inventors of the present disclosure found the following matter. In a vane pump in the related art, air bubbles gather in the center of a whirl of oil that is caused when the oil flows from a discharge port into a pump chamber via a whisker groove. When the air bubbles crush, large impact is caused, so that erosion occurs in a sideplate. Further, as the density of the air bubbles is larger, large erosion occurs. The inventors obtain such an insight that, when the magnitude (diameter) of the whirl of the oil is made larger, the density of the air bubbles decreases, thereby making it possible to restrain occurrence of large erosion.

With reference FIGS. 6A, 6B, next will be described a configuration of the present embodiment in which the whirl of the oil is made large to decrease the density of air bubbles so that large erosion is restrained from occurring on the pump chamber forming surface 4 a. Further, here, the configuration of the first extension groove 45 will be described mainly. However, the second extension groove 46 is also configured similarly to the first extension groove 45.

FIG. 6A is a partial enlarged view of FIG. 1 and illustrates the first extension groove 45 and its peripheral part. FIG. 6B is an enlarged view illustrating a part VIB in FIG. 6A in a further enlarged manner. In FIGS. 6A, 6B, a virtual extension line 90 obtained by further extending a center line 45 a of the groove width of the first extension groove 45 from a distal end part 452 of the first extension groove 45 is indicated by an alternate long and two short dashes line, and a belt-shaped range 91 obtained by extending a groove width W of a base end part 451 of the first extension groove 45 along the center line 45 a and the virtual extension line 90 is indicated by gray hatching. The center line 45 a is a group of points (a perpendicular bisector of a line segment corresponding to the groove width) that divides the groove width of the first extension groove 45 in half, the groove width being a width in a direction perpendicular to the extension direction of the first extension groove 45. The groove width W is a maximum value of the groove width of the first extension groove 45.

The groove width of the first extension groove 45 is gradually narrowed from the base end part 451 on the first discharge port 43 side toward the distal end part 452, and the shape of a section of the first extension groove 45, the section being perpendicular to the longitudinal direction (the extending direction) of the first extension groove 45 is a triangular V-valley shape. A groove bottom 450 as a bottom of the V valley has a linear shape inclined such that the distal end part 452 is closer to the side face 5 b of the rotor 5 than the base end part 451. When the pump chamber forming surface 4 a is viewed from the axial direction, the center line 45 a overlaps with the groove bottom 450. The groove depth of the first extension groove 45 as a distance between the pump chamber forming surface 4 a and the groove bottom 450 in a direction perpendicular to the pump chamber forming surface 4 a becomes gradually shallower from the base end part 451 toward the distal end part 452.

FIG. 6A illustrates a state where, out of paired vanes 6 defining the pump chamber S communicating with the first extension groove 45, the vane 6 on the front side in the rotation direction of the rotor 5 has passed the base end part 451 of the first extension groove 45. In this state, the vane 6 on the rear side in the rotation direction out of the paired vanes 6 defining the pump chamber S is placed near the distal end part 452 of the first extension groove 45. In the following description, one of the paired vanes 6 that is on the front side in the rotation direction from the pump chamber S is referred to as a first vane 61, and the other one of the paired vanes 6 that is on the rear side in the rotation direction is referred to as a second vane 62. Further, the pump chamber S defined by the first vane 61 and the second vane 62 is referred to as a pump chamber S₁.

The pressure of the pump chamber S₁ gradually increases by the oil flowing into the pump chamber S₁ from the first discharge port 43 via the first extension groove 45 while the rotor 5 rotates with the first vane 61 crossing the first extension groove 45 in an axial view. When the first vane 61 passes the base end part 451 of the first extension groove 45 and the pump chamber S₁ communicates with the first discharge port 43, the pressure of the pump chamber S₁ rapidly increases. The oil flowing into the pump chamber S₁ from the first extension groove 45 becomes a jet flow and forms a whirl inside the pump chamber S₁, so that minute air bubbles gather in the central part of the whirl.

The air bubbles crush due to the increase in the pressure of the oil when the pump chamber S₁ communicates with the first discharge port 43. In FIG. 6A, the rotation direction and the magnitude of the whirl are expressed by an arrow 92.

As described above, in order to restrain the occurrence of large erosion on the pump chamber forming surface 4 a, it is desirable to increase the magnitude of the whirl caused by the oil flowing into the pump chamber S₁ from the first extension groove 45. In the present embodiment, in order to restrain the occurrence of erosion due to the crush of the air bubbles in the pump chamber S₁, the shape of the sideplate 4 is configured as follows. That is, when the pump chamber forming surface 4 a is viewed from the axial direction at the time when the first vane 61 passes the base end part 451 of the first extension groove 45, the shape of the sideplate 4 satisfies the following requirements (1) to (5). (1) The center line 45 a of the groove width of the first extension groove 45 is inclined from the radial direction of the rotor 5 (a direction indicated by an alternate long and short dash line RD in FIG. 6A) such that the center line 45 a approaches the rotation axis O of the rotor 5 on the distal end part 452 side rather than the base end part 451 side. (2) An open end 511 of the slit 51 in which the second vane 62 is accommodated falls within the belt-shaped range 91. (3) The virtual extension line 90 does not intersect with the rotor 5 between the first vane 61 and the second vane 62. (4) Among angles formed between the virtual extension line 90 and the second vane 62, an angle θ₁ on the first vane 61 side and on the cam surface 3 a side falls within a range of 90°±10°. (5) The distal end part 452 of the first extension groove 45 is placed, in the radial direction of the rotor 5, outwardly from the protrusion 53 in the opening peripheral part of the slit 51 in which the second vane 62 is accommodated.

The requirement (1) indicates, in other words, that the first extension groove 45 from the base end part 451 to the distal end part 452 faces the inside of the rotor chamber 30. The base end part 451 of the first extension groove 45 communicates with an end part region of the first discharge port 43, the end part region being on the cam surface 3 a side. The distal end part 452 of the first extension groove 45 is placed to be further closer to the rotation axis O than a part of a connection portion between the first extension groove 45 and the first discharge port 43, the part being closest to the rotor 5 side.

The requirement (2) indicates that, when a jet flow with the groove width W that is a maximum width of the first extension groove 45 occurs along the center line 45 a and the virtual extension line 90, the jet flow hits an area around the open end 511 of the slit 51 in which the second vane 62 is accommodated. More specifically, the jet flow hits a corner part between a surface 62 a, on the first vane 61 side, of the second vane 62 and the top surface 53 a of the protrusion 53.

In the present embodiment, when the requirements (1) and (2) are satisfied, the magnitude of the whirl caused by the oil flowing into the pump chamber S₁ from the first extension groove 45 is large, and the flow of the whirl is weak in comparison with a comparative example illustrated in FIGS. 7A, 7B (describe later), for example. An action of increasing the magnitude of the whirl is obtained when a large space is formed between the cam surface 3 a and each of the center line 45 a and the virtual extension line 90. An action of weakening the flow of the whirl is obtained as follows. That is, when the first extension groove 45 faces the inside of the rotor chamber 30, an angle at which the jet flow hits the surface 62 a of the second vane 62 is near 90°, so that unidirectionality of the flow of the oil after the jet flow hits the second vane 62 is relaxed, thereby resulting in that the oil is easily dispersed in multiple directions. Thus, the action of weakening the flow of the whirl is obtained. These actions can restrain minute air bubbles from gathering within a small range in a central part of the whirl, thereby making it possible to yield an effect to restrain occurrence of erosion.

The requirement (3) indicates that the jet flow with the groove width W from the first extension groove 45 mainly hits the vicinity of a base (the vicinity of the open end 511) of the second vane 62 projecting from the slit 51. Hereby, a strong whirl can be hardly caused in comparison with a case where the jet flow at the time when the first vane 61 passes the base end part 451 of the first extension groove 45 mainly hits the inclined surface 53 b of the protrusion 53 of the rotor 5.

The requirement (4) indicates that the angle θ₁ falls within a range where a strong whirl of the oil can be hardly caused by the jet flow. A most ideal value of the angle θ₁ is 90°. However, when the angle θ₁ is within a range of 80° or more but 100° or less, the oil that becomes a jet flow is easy dispersed, so that a whirl of the oil with a strong flow can be hardly caused.

The requirement (5) indicates that the first extension groove 45 extends to a circumferential position at which the first extension groove 45 reaches an outer part of the protrusion 53 in the radial direction of the rotor 5. Hereby, it is possible to control the flow direction of the oil flowing into the pump chamber S₁ from the first extension groove 45 over a long range. This allows the jet flow to be guided to the vicinity of the open end 511 of the slit 51. FIG. 6B illustrates a case where the first extension groove 45 extends to a position placed radially outwardly from the top surface 53 a of the protrusion 53, as one example.

Note that it is desirable that the position of the distal end part 452 of the first extension groove 45 at the time when the first vane 61 passes the base end part 451 of the first extension groove 45 be on the first vane 61 side from the surface 62 a of the second vane 62, from the viewpoint of preventing the first extension groove 45 from communicating with the first inlet port 41 via the pump chamber S on the rear side in the rotation direction from the pump chamber S₁.

Comparative Example

FIG. 7A is a configuration diagram illustrating part of a vane pump 1A according to a comparative example, and FIG. 7B is an enlarged view illustrating a part VIIB in FIG. 7A in an enlarged manner. In FIGS. 7A, 7B, constituents common to those described in the above embodiment have the same reference signs used in FIGS. 6A, 6B, and redundant descriptions are omitted.

In the vane pump 1A according to the comparative example, the inclination angle of a first extension groove 45A from the radial direction of the rotor 5, the first extension groove 45A being extended from the first discharge port 43, is different from the inclination angle of the first extension groove 45 from the radial direction of the rotor 5 in the above embodiment, and the first extension groove 45A is formed to extend along the rotation direction of the rotor 5. That is, the distal end part 452 of the first extension groove 45A is placed at a position distanced from the rotation axis O as compared to that in the above embodiment. In this configuration, among the angles formed between the virtual extension line 90 and the second vane 62, an angle θ₂ on the cam surface 3 a side becomes large, the oil flowing along the surface 62 a of the second vane 62 easily causes a strong whirl, and the space between the cam surface 3 a and each of the center line 45 a of the first extension groove 45A and the virtual extension line 90 becomes small, so that the magnitude of the whirl to be caused becomes small. Accordingly, air bubbles gather in the central part of the whirl at a high density, so that erosion easily occurs. In FIG. 7A, the rotation direction and the magnitude of the whirl are expressed by an arrow 93.

On the other hand, in the above embodiment, the shape of the sideplate 4 is configured to satisfy the above requirements (1) to (5). Accordingly, it is possible to restrain occurrence of erosion more effectively than the vane pump 1A according to the comparative example.

Additional Matters

The present disclosure has been described based on the embodiment, but the embodiment described above does not limit the disclosure according to Claims. Further, it should be noted that all combinations of features described in the embodiment may not necessarily be essential to the means for solving the problem of the disclosure.

Further, the present disclosure can be carried out by appropriately modifying the present disclosure by omitting some configurations or adding or replacing configurations within a range that does not deviate from the gist of the present disclosure. For example, the shape of the sideplate 4 may not necessarily satisfy the requirements (3) to (5) among the requirements (1) to (5), provided that the shape of the sideplate 4 satisfies at least the requirements (1) and (2). 

What is claimed is:
 1. A vane pump comprising: a cam ring having a cam surface on an inner peripheral surface of the cam ring, the cam ring forming a rotor chamber; a rotor configured to rotate in a predetermined rotation direction inside the rotor chamber, the rotor including a plurality of slits formed in a radial manner to extend radially outwardly from a central part of the rotor; a plurality of vanes provided such that the vanes are accommodated in the slits, respectively, and rotate together with the rotor, the vanes being configured to define a plurality of pump chambers between the cam surface and an outer peripheral surface of the rotor; and a lateral plate having a flat pump chamber forming surface facing the pump chambers, the lateral plate being configured such that an inlet port via which a fluid is taken into the rotor chamber and a discharge port via which the fluid taken into the rotor chamber is discharged are opened on the pump chamber forming surface, wherein: the lateral plate has an extension groove extended rearward in the rotation direction from the discharge port, the extension groove having a groove width gradually narrowed from a base end part, on the discharge port side, of the extension groove toward a distal end part of the extension groove; at a time when a first vane out of paired vanes defining a pump chamber communicating with the extension groove, the first vane being on a front side in the rotation direction of the rotor, passes the base end part of the extension groove, the pump chamber forming surface viewed from a rotation-axis direction of the rotor has a shape satisfying the following requirements i) and ii), i) a center line of the groove width of the extension groove is inclined from a radial direction of the rotor such that the center line approaches a rotation axis of the rotor on the distal end part side rather than the base end part side, and ii) among the slits, a slit in which a second vane out of the paired vanes, the second vane being on a rear side in the rotation direction, is accommodated has an open end falling within a belt-shaped range obtained by extending a groove width of the base end part of the extension groove along a virtual extension line obtained by further extending a center line of the groove width of the extension groove from the distal end part.
 2. The vane pump according to claim 1, wherein the shape of the pump chamber forming surface viewed from the rotation-axis direction of the rotor further satisfies the following requirement iii) at the time when the first vane passes the base end part of the extension groove, iii) the virtual extension line does not intersect with the rotor between the first vane and the second vane.
 3. The vane pump according to claim 1, wherein the shape of the pump chamber forming surface viewed from the rotation-axis direction of the rotor further satisfies the following requirement iv) at the time when the first vane passes the base end part of the extension groove, iv) among angles formed between the virtual extension line and the second vane, an angle on the first vane side and on the cam surface side falls within a range of 90°±10°.
 4. The vane pump according to claim 1, wherein: an opening peripheral part of each of the slits in the rotor is formed as a protrusion projecting radially outwardly from a circumferential central part between two adjacent slits among the slits; and the shape of the pump chamber forming surface viewed from the rotation-axis direction of the rotor further satisfies the following requirement v) at the time when the first vane passes the base end part of the extension groove, v) the distal end part of the extension groove is placed radially outwardly from the opening peripheral part in the radial direction of the rotor. 